Two sides of a coin: Batman (Christian Bale) returns to face the late Heath Ledger as the maniacal Joker in The Dark Knight.

The Dark Knight

Opens Friday, July 18, at multiple locations.

What a brooding pleasure it is to return to Christopher Nolan's Gotham City — if "pleasure" is the right word for a movie that gazes so deeply and sometimes despairingly into the souls of restless men. In The Dark Knight, the continuation of Nolan's superb 2005 reboot of the Batman franchise, Batman Begins, fair Gotham is a modestly cleaner, better-lit place than it was when last we saw it, if still a far stretch from the shining city on a hill its winged protector believes it can be.

A superhero movie of unusual psychological complexity, Batman Begins was, in the tradition of all such origin stories, about a heretofore-ordinary man coming into a heightened sense of his super-ego. But Nolan, who has one of the great procedural minds among contemporary filmmakers, was hardly content to offer up the death of a young boy's parents as a tidy Freudian backstory for what turns a Bruce Wayne into a Batman. Instead, Nolan's Batman (played with iron-jawed intensity by Christian Bale) was the product of many wayward years in the wilderness followed by still more years of rigorous training at the hands of a Svengali-like master, Ra's Al Ghul. Only then, quite late in the day (and the running time), was young Wayne ready to become Batman. At which point, in a twist that now seems perhaps a touch too Shakespearean (by way of George Lucas), the pupil found himself forced to use the master's teachings against the master himself.

In The Dark Knight, nothing is nearly so cut-and-dried. Whereas the radicalized Ra's, with his arsenal of dirty bombs and his urge to eradicate Western "decadence," was a supervillain of the sort that anyone who reads the papers has been conditioned to expect, the Joker of The Dark Knight is all the more terrifying for not having a plan or an identifiable motive. A committed anarchist in a dusting of floury foundation, a smear of crimson lipstick and pools of Louise Brooks eye shadow, this Joker isn't the ebullient prankster of Batman movies (and TV shows) past, but rather a freakishly disturbing embodiment of those destructive human impulses that can't so easily be explained away. His only rule is to show others the folly of rules, the absurdity of striving to impose order upon chaos. "Some men just want to watch the world burn," observes the ever-wise butler Alfred (Michael Caine). Except that this Joker doesn't merely want to watch; he wants to strike the match.

By now, of course, you know that the Joker is played by Heath Ledger in the last role he completed before his death, this past January, at the age of 28. And it is perhaps the best compliment one can pay to this gifted young actor to say that his performance here would have cemented his legend even if he'd lived to see the film's release. The Joker enters into The Dark Knight gradually, at first a tangential figure in a not particularly interesting Mafia money-laundering subplot. But even then, Ledger seems to make the film grow larger whenever he's onscreen (no matter if you happen to already be watching it in the giant-screen IMAX format). Having shown a penchant for the chameleonic as the sensitive, soft-spoken cowpoke of Brokeback Mountain and the terminally good-vibrating surf-shop owner of Lords of Dogtown, Ledger here again invests in a character from the inside-out, lending the Joker's every physical tick and vocal inflection a signature flair.

No wonder Ledger was reportedly exhausted after finishing work on the film; watching him, you can see how demanding he was on himself, how much he refused to play any predictable beats, whether the Joker is casually advising a room of armed thugs to not "blow things out of proportion" while outfitted in the latest in suicide-bomber haute couture, or slicking his hair back with his hands and sashaying across the dance floor to greet the comely assistant D.A. Rachel Dawes (Maggie Gyllenhaal, less milquetoast than Katie Holmes). But the genius of the performance is how fully Ledger convinces us that the Joker is capable of doing anything at any moment — even, if the occasion calls for it, to stop being the Joker.

In making the transition from low-budget independent films to studio tentpole projects, Nolan (who co-authored The Dark Knight with his brother, Jonathan), has sacrificed none of his abiding obsessions. Like the amnesiac amateur detective who occupied the central role in Nolan's Möbius-strip sophomore feature, Memento, the Bruce Wayne of Dark Knight is increasingly gripped by an existential crisis, wondering whether he is the hero or the villain of his own story. And like the rival illusionists of Nolan's 2006 film The Prestige, the longer Batman and the Joker engage in their battle of wills — the one confident in the inherent goodness of mankind, the other equally certain that man is but a savage beast — the more the distance collapses between them. Triangulating their position is D.A. Harvey Dent (played with gleaming, Kennedy-esque righteousness by Aaron Eckhart).

That makes The Dark Knight sound like heavy stuff — and it is. But I should add that Nolan also delivers the kick-ass goods, from an opening bank heist à la Michael Mann to a climactic episode of vehicular mayhem à la William Friedkin. So The Dark Knight will give your adrenal glands their desired workout, but it will occupy your mind, too, and even lead it down some dim alleyways where most Hollywood movies fear to tread. By the end of this second installment in that rare franchise one hopes won't end anytime soon, Batman seems to have less in common with his superhero brethren than with those old frontiersmen of movies past. Like The Searchers' Ethan Edwards and High Noon's Will Kane, he's left to ride off into the darkness, pondering the uncertain destiny of principled men in an unprincipled world — as are we.